Refrigeration cycle apparatus

Abstract

A refrigeration cycle apparatus ( 50 ) includes: a main refrigerant circuit ( 21 ) having a compressor ( 1 ), a radiator ( 2 ), a first expansion mechanism ( 5 ), a second expansion mechanism ( 6 ), and an evaporator ( 4 ); an injection passage ( 22 ) for supplying an intermediate-pressure refrigerant to an injection port 1 c of the compressor 1 ; and a water circuit ( 30 ) through which water to be heated in the radiator ( 2 ) flows. The refrigeration cycle apparatus ( 50 ) includes a sub heat exchanger ( 3 ) for cooling the water in the water circuit ( 30 ) by exchanging heat between the refrigerant in the injection passage ( 22 ) and the water to be heated in the radiator ( 2 ).

The invention claimed is: 
     
       1. A refrigeration cycle apparatus comprising:
 a main refrigerant circuit having a compressor provided with an injection portion, a radiator that heats fluid, a first expansion mechanism, a second expansion mechanism, and an evaporator, which are connected in a circuit in this order; 
 an injection passage connecting the injection portion of the compressor to a portion of the main refrigerant circuit between the first expansion mechanism and the second expansion mechanism; 
 a fluid circuit through which the fluid, which is heated in the radiator by a refrigerant in the main refrigerant circuit, flows; and 
 a sub heat exchanger that is a liquid-liquid heat exchanger, which comprises a low-temperature side flow passage and a high-temperature side flow passage, cools the fluid flowing in the high-temperature side flow passage, and heats the refrigerant flowing in the low-temperature side flow passage by exchanging heat between the refrigerant and the fluid before the fluid is heated in the radiator, 
 wherein the sub heat exchanger is disposed in the injection passage, 
 a flow rate regulator that regulates a flow rate of the refrigerant, which flows from the main refrigerant circuit into the injection passage, into the sub heat exchanger by adjustment of an opening degree of the flow rate regulator, is further disposed in the injection passage, wherein the regulating the flow rate of the refrigerant includes closing an opening for the flow of the refrigerant into the sub heat exchanger, and 
 the sub heat exchanger is located between the flow rate regulator and the compressor. 
 
     
     
       2. The refrigeration cycle apparatus according to  claim 1 , wherein the compressor provided with the injection portion has an injection port that injects the refrigerant from the injection passage into a compression chamber. 
     
     
       3. The refrigeration cycle apparatus according to  claim 1 , wherein:
 the compressor is a multi-stage compressor including a low-pressure compression mechanism, a high-pressure compression mechanism, and a flow passage connecting an outlet of the low-pressure compression mechanism and an inlet of the high-pressure compression mechanism; 
 wherein the flow passage is the injection portion of the compressor. 
 
     
     
       4. The refrigeration cycle apparatus according to  claim 1 , further comprising:
 a controller that controls the flow rate regulator and at least one mechanism selected from the group consisting of the first expansion mechanism and the second expansion mechanism, based on a flow rate and a temperature of the fluid in the sub heat exchanger. 
 
     
     
       5. The refrigeration cycle apparatus according to  claim 1 , wherein the refrigerant is carbon dioxide. 
     
     
       6. The refrigeration cycle apparatus according to  claim 1 , wherein the fluid is water,
 the fluid circuit comprises a hot water storage tank and a heat exchanger that heats space, and 
 the refrigeration cycle apparatus is a multi-functional heat pump that is capable of heating water and space simultaneously. 
 
     
     
       7. The refrigeration cycle apparatus according to  claim 6 , wherein the heat exchanger that heats the space is an indoor radiator that performs the space heating by circulating hot water having been stored in the hot water storage tank, and
 the fluid circuit comprises:
 (a) a space heating water circuit, which includes the indoor radiator; and 
 (b) a heat source side water circuit that is connected to the space heating water circuit, the sub heat exchanger, which cools return water that has flowed from the indoor radiator, and the radiator, which heats thereafter the cooled return water. 
 
 
     
     
       8. The refrigeration cycle apparatus according to  claim 6 , wherein the heat exchanger that heats the space is an indoor radiator that performs the space heating by circulating hot water stored in the hot water storage tank, and the fluid circuit comprises:
 (a) a space heating water circuit, which includes the indoor radiator; and 
 (b) a heat source side water circuit in which water having been stored in a lower part of the hot water storage tank is cooled in the sub heat exchanger and thereafter heated in the radiator. 
 
     
     
       9. The refrigeration cycle apparatus according to  claim 8 , wherein the heat source side water circuit comprises:
 a main passage including the sub heat exchanger; and 
 a bypass passage that branches off from the main passage at an upstream side relative to the sub heat exchanger and merges with the main passage between the sub heat exchanger and the radiator at a downstream side relative to the sub heat exchanger; and 
 a flow of water in the heat source side water circuit is switched between a first state in which the water in the heat source side water circuit flows only through the main passage and a second state in which the water flows only through the bypass passage. 
 
     
     
       10. The refrigeration cycle apparatus according to  claim 9 , further comprising:
 a switching valve that switches the flow of the water in the heat source side water circuit between the first state and the second state; and 
 a controller that controls the flow rate regulator and the switching valve, 
 wherein the controller performs a control of the flow rate regulator and a control of the switching valve by associating the control of the flow rate regulator and the control of the switching valve with each other so that the water flows only through the bypass passage when the flow rate of the refrigerant in the injection passage is zero. 
 
     
     
       11. The refrigeration cycle apparatus according to  claim 8 , wherein a downstream end of the space heating water circuit is connected to a portion of the heat source side water circuit at an upstream side relative to the sub heat exchanger so that return water that has flowed from the indoor radiator is heated in the radiator after passing through the sub heat exchanger.